Railway signaling system



Nov. 23, 1943.

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2 Ba 1 fiy H was a 5 5% u .QQNN $3 5% kg QQN Patented Nov. 23, 1943 72,335,151 RAILWAY SIGNALING SYSTEM Ralph E.

The Union Kemmerer, Swissvale, Pa., assignor to Switch & Signal Company,Swissvale, Pa., a corporation of Pennsylvania Application July 30, 1942,

Serial No. 452,893

14 Claims. (01. 246-38) My invention relates to railway signalingsystems of the type employing wayside signals of the searchlight type.

In some systems where more than two proceed indications are desired thewayside signals employ upper and lower units each comprising asearchlight signal unit. These signal units cooperate to provide thevarious indications. However, only certain combinations of aspects ofthe two signal units are authorized. It is desired to check response ofthe signals to determine if they are displaying the proper aspects, andto govern the supply of signal control energy to the adjacent section inthe rear so that if a signal is displaying an unauthorized indicationthe adjacent signal in the rear will be prevented from displaying itsleast restrictive indication.

' An object of my invention is to provide an improved railway signalingsystem of the type employing wayside signals having two Searchlightsignal units, the system being arranged so that the signals are checkedto determine if they are displaying the proper aspects.

Another object of the invention is to provide a system of the typedescribed and having means governed by the signals and controlling thesupply of energy to the adjacent section in the rear.

A further object of the invention is to provide a signaling system ofthe type described in which one of the signal units controls the supplyergy to the other signal unit to thereby prevent the display of anunauthorized combination of aspects by the two signal units.

Another object of the invention is to provide a system of the type meansto delay certain types of changes in the signals to thereby preventmomentary display of incorrect or unecessarily restrictive aspects bythe signals.

Other objects of the invention and features of novelty will be apparentfrom the following description takenin connection with the accompanyingdrawings.

I shall describe four forms of apparatus embodying my invention andshall then point out the novel features thereof in claims.

In practicing my invention I provide repeater relays to detect responseof the signal units to changes in the signal control relays and I employthese repeater relays of energy to the adjacent section in the rear. Insome modifications these repeater relays directly control the supply ofenergy to the section in the rear, and in other modifications therepeater relays control the supply of energy to the section ofendescribed and incorporating to control the supply a in the rearthrough a checking relay which checks correspondence between the signalcontrol and signal repeater relays. In addition, in some modificationsthe signal repeater relays for the upper signal unit control the supplyof energy to the winding of the lower signal unit, while in each of themodifications the lightout relay for the upper unit of a signal controlsthe polarity of the energy supplied to the lower unit ofthe signal sothat energy effective to cause the lower unit of the signal to display agreen light cannot be supplied to the winding of this unit if the lampof the upper unit of the signal is burned out. In some modifications .ofthe invention the green repeater relay for each signal unit is slow inreleasing and when picked up establishes a circuit to supply energy tothe winding of the associated signal unit to delay changes in'thissignal unit until the signal control relays respond to changes intraific conditions and thus prevent the momentary display ofunnecessarily restrictive indications.

In the drawings Figs. 1 and 3 are diagrams of systems embody-' ing myinvention and having wayside signals arranged to provide four aspects,and I Figs. 2 and 4 are diagrams of signaling systems also embodying myinvention and having wayside signals arranged to provide five aspects.

Similar reference characters refer to similar parts in each of theseveral views.

Referring to Fig. 1 of the drawings there is shown therein a stretch ofrailroad track having track rails I and 2 over which traffic normallymoves in the direction indicated by the arrow, that is, from left toright. The rails of the track stretch are separated by insulated joints3 into the customary successive track sections, and the rails of each ofthese sections form a part of a track circuit of the usual character.

The system shown employs alternating current energy in the trackcircuits. This energy may be derived from any suitable source and may bedistributed throughout the track stretch by a transmission line, notshown. In the drawings the termnals of the power supply source aredesignated BX and CK.

In the diagram forming Fig. 1 of the drawings one complete tracksection, designated IZT, and parts of two adjoining sections HT and I31,are shown. Each of these section has located at the entrance end thereofa with an appropriate prefix, for governing trafiic in the track'stretch. Each of these signals has an upper unit SU, and a lower unitSL, each comsignal designated S l prising a familiar searchlight signalunit. Each the rectifier HR to track relay IZTR and proof these signalsis provided with a mechanism duces code following operation of thisrelay with capable of selectively projecting a plurality of the resultthat the two portions of the decoding beams of light of different colorsfrom a single transformer primary winding are alternately enlightsource. The construction of the signal 5 ergized and energy is inducedin the transformer units is not a part of this invention and thesesecondary windings.

units may be of any well known construction. Energy from one of thesewindings is rectified A signal unit of the type which I may employ is bya contact of the track relay and is supplied shown in Letters Patent ofthe United States No. to relay l2I-I, while energy from the othertransl,864,224, granted June 21, 1932, to Wesley B. former secondarywinding is supplied through Wells. resonant rectifier unit lfiilDU torelay IZJ.

The signaling system shown in Fig. 1 is of the As the relays IZH and ENare picked u enfour indication variety and makes use of track ergy ofnormal polarity is supplied to the windcircuit energy coded at threedifferent frequen.-- ing of signal I2SU over the circuit which is cies.This coded energy is provided by code transtraced from terminal Bthrough front contact conditions ahead. In the illustrative form nal .0.Accordingly, the signal mechanism conshown, each code transmitter CT isprovided with ditions the signal to provide its green indication,

three circuit making and breaking contacts 75, while the contact G ofthe signal is closed so that 120 and 180 which are continuously actuatedby energy is supplied to the relay EZUG and its cona motor or othersuitable mechanism at three diftacts are picked up so that its contactinterferent speeds. For purposes of illustration it will rupts thecircuit of the winding of signal lZSL.

' be assumed that these speeds are such as to pro- 25 At this time, assignal IZSU is displaying its green vide 75, 120 and 180 energy pulsesper minute indication, relay lZUY is released and its contacts which areseparated by periods of equal duration 27 and 28 additionally interruptthe circuit of in which no energy is supplied. the winding of signalIZSL. Accordingly, the Each of the track sections includes a codefolsignal IZSL displays its red indication so the si lowing track relaydesignated TR together with 30 nal I28 displays its clear indicationconsisting an appropriate prefix. The track relay is located of a greenlight over a red light. at the entrance end of the track section and mayAs relays H and l UG are picked up, ener y be of any suitable type. Asshown, the track of 180 code frequency is supplied to track transrelay I2TR is of the direct current type and is former HTT over the circuitwhich is traced connected to the track rails through a suitable '35 fromterminal BX through contact 180 of code rectifier I 2R. The track relayIZTR has assotransmitter I ZCT, front contact 3!! of relay IZUG, ciatedtherewith a decoding transformer ILZDT, front contact 3| of relay IZH,and prima y Wi dsignal control relays 42H, NJ and I 2K, signal reing oftransformer l ITT to terminal CX. Acpeater relays I 2UG, I 2UY and IZLG,and a cordingly, energy of 180 code frequency is suplightout relayIZULO. plied to the rails of section HT and the signal The relays IN and12K are energized from the for this section displays its clearindication.

, capacitance which are arranged and propor- 45 out relay IZULO so thatthis relay is picked up tioned so that when the frequency of the currentas long as the lamp filament is intact.

supplied thereto is that present when the track When a train moving inthe normal direction relay is responding to energy of a particular codeof trailic enters section IZT, the track relay iZ'I'R frequencysuflicient energy is supplied through is shunted and relays 121-1 andl2J release. On the unit to pick up the associated relay. Each releaseof relay IZH its contacts 20 and 23 inunit is also arranged so that whenenergy of a terrupt the supply of energy to the winding of sociatedrelay U0 p ck up its contacts Each of IZH are released energy cannot besupplied to these units includes a rectifier which rectifies signal I2SLso it continues to display its red the energy supplied through the unit.indication. Accordingly, signal lZS displays its The elements of theunit I ZODU are proporstop indication consisting of a red light over ationed so that the 1elay'l2K is picked up when a red light. a

the track relay is responding to ener y of 120 When the signal IZSUdisplays its red indicacode frequency, while the elements of the unittion its contact G interrupts the circuit of the lBllDU are proportionedso that the relay IZJ relay I ZUG, while at this time the circuit ofthis is picked up when the track relay is responding relay isadditionally interrupted by contact 33 .r

to energy of 180 code frequency. of relay IZJ.

Each of the signals has associated therewith On release of relay l2H itscontact 3| interasource of direct current, such as a storage 'batruptsthe supply of energy of 180 code fretery, not shown, the terminals ofwhich are desigquency to the transformer HTT and establishes nated B andC. the circuit for supplying energy of code fre- The equipment is shownin the condition which quency thereto. it assumes when the trackstretchis vacant. At When the train advances into section I3T the this time,energy of code frequency is sup- 70 signal for that section is caused-todisplay its which supplies energy to the track transformer feeds torelay I ZIR and the relay causes energy I HTT for section HT, Thisenergy feeds through 7 5 to be supplied through the decodingtransformer.

assar |2DT to the relay |2H so that its contacts are picked up. The rateof operation of the track relay |2TR on '75 code is such that energy isnot supplied through the units |80DU and |20DU and the relays |2J and|2K remain released.

When relay |2H picks up, its contacts 2|) and 23 establish a circuit tosupply energy of reverse polarity to the winding of signal |2SU. Thiscircuit is traced from terminal B through front contact 20 of relayIZI-I, back contact 34 of relay HUG, back contact 22 of relay |2J,winding of signal |2S back contact 2| of relay |2J, back contact 35 ofrelay IZUG, and front contact 23 of relay |2H to terminal C. This energycauses the signal mechanism to condition the signal to display itsyellow indication, while the front contact Y of the signal'is closed toestablish the circuit to supply energy to the relay |2UY and contacts 21and 28 of this relay are picked up. However, at this time the contactsof relays |2LG and |2K are released so the circuit of the winding ofsignal |2SL is interrupted and this signal continues to display its redindication. Accordingly, the signal |2S now displays its approachindication consisting of a yellow light over a red light.

On picking up of the contacts of relay IZH its contact 3| interrupts thesupply of energy of 7 code frequency to section HT and establishes thecircuit to supply energy of 120 code frequency thereto. This circuit iscompleted on picking up of relay |2UY and is traced from terminal BXthrough contact I of code transmitter |2CT, front contact 31 of relayIZUY, back contact 38 of relay |2LG, back contact 30 of relay IZUG,front contact 3| of relay |2H, and primary winding of transformer ||TTto terminal CX. It will be seen that the circuit for supplying energy of120 code frequency to section ||T includes contacts of the signalrepeater relays |2LG and |2UG so that this circuit will not beestablished if the lower signal |2SL should improperly display its greenindication or the upper signal |2SU should improperly display its greenindication.

When the train advances far enough to vacate section |3T the signal forthat section is conditioned to display its approach indication, whileenergy of 120 code frequency is supplied to the rails of section |2T.This energy feeds to relay |ZTR and operates it at a rate such thatenergy is supplied through the unit |20DU and picks up the relay |2K sothat its contacts 4|] and 4| establish the circuit to supply energy ofnormal polarity to the winding cuit for supplying energy to signal |2SLis traced from terminal B through front contact 20 of relay IZH, backcontact of relay IZUG, front contact 42 of relay I2ULO, front contact 40of relay IZK, front contact 21 of relay |2UY, winding of signal |2SL,front contact 28 of relay IZUY, front contact 4| of relay IZK, frontcontact 43 of relay H.710, and front contact 23 of relay |2H to terminalC. The energy of normal polarity supplied to signal |2SL causes thesignal mechanism to condition the signal to provide its green indicationso that the signal |2S displays its approach medium indicationconsisting of a yellow light over a green light.

It will be seen that the circuit for supplying energy of normal polarityto the winding of signal |2SL includes front contacts 42 and 43 oflightout relay IZULO. If the lamp of the upper signal is burned out, thecontacts of relay |2ULO will be released and will cause the energysupplied of signal I2SL. The cirof code frequency is to the winding ofsignal |2SL to be of reverse polarity so that the signal mechanism willcondition the signal to provide a yellow instead of a green light. Thisarrangement prevents the lower signal unit |2SL from displaying a greenlight when the lamp of the upper signal unit IZSU is burned out. Thisprevents the display of a single green light by a signal when the lampof the upper signal unit is burned out, and causes a single yellow lightto be displayed at such times. The single green light might beinterpreted as a clear indication when the signal is intended to displayits approach medium indication, while the single yellow light will beinterpreted as a more restrictive indication than that intended to bedisplayed by the signal.

When the mechanism of signal |2SL responds to energization of the signalwinding by current of normal polarity, front contact G of the signal isclosed and establishes the circuit to supply energy to the relay IZLG sothat contact 38 of this relay picks up and interrupts the supply ofenergy of 120 code frequency to transformer ||TT and establishes acircuit to supply energy of code frequency thereto. This circuit istraced from terminal BX through contact I86 of the code transmitter,front contact 38 of relay |2LG, back contact 38 of relay |2UG, frontcontact 3| of relay IZH, and primary winding of transformer ||TT toterminal CX. The energy of 180 code frequency supplied to the rails ofsection IT causes the signal for that section to provide its clearindication.

If the lamp of the upper signal unit is burned out so relay IEULO isreleased and signal IZSL displays its yellow indication, relay |2LG willnot be energized and its contact 38 will not establish the circuit forsupplying energy of 180 code frequency to section HT, but will maintainthe circuit for supplying energy of 120 code frequency thereto.Accordingly, the signal for section T will not provide its clearindication but" will display its approach medium indication, and afollowing train will receive a restrictive indication before it reachesthe signal |2S at a time when that signal is displaying a single yellowlight.

When the train under consideration vacates the section in advance ofsection |3T energy supplied to the rails of section |3T and the signal|3S displays its approach medium indication, while energy of 180 codefrequency is supplied to the rails of section |2T. This energy feeds tothe track relay |2TR and operates it at a rate such that energy is nolonger supplied through unit IZQDU to relay IZK but is supplied throughunit IBGDU to relay |2J.

When relay |2J picks up, its contacts 2| and 22 interrupt the previouslytraced circuit for supplying energy of reverse pdlarity to the windingof signal |2SU and establish the circuit for supplying energy of normalpolarity thereto, while contact 33 of relay |2J establishes the circuitfor relay |2UG so that energy is supplied to this relay over the circuitwhich includes front contact G of the signal. When relay IZUG picks up,its contact 25 interrupts the circuit oi signal IZSL and this signaldisplays a red light, while contact 30 of the relay IZUG interrupts onecircuit for supplying energy of 180 code frequency to section HT andestablishes another circuit for supplying energy of 180 code frequencythereto.

When the energy supplied to section |2T is changed from 120 to 180 codefrequency the re lay IZK releases and the relay lZJ picks up. The relayIZK may release before the signal IZSU responds to picking up of relayIZJ, and this system is arranged to prevent an undesirable flash of theapproach indication at such times.

When energy of 120 code frequency is supplied to section I2T the relays1 2H and IZK are picked up while the relay I2J is released so thatenergy of normal polarity is supplied to the winding of signal I2SL overthe circuit which is traced from terminal B through front contact 29 ofrelay lZI-I, back contact 25 of relay lZUG, front contact 42 of relayI2ULO, front contact 40 of relay IZK, front contact 27 of relay IZUY,winding of signal I ZSL, front contact 28 of relay IZUY, front contact4! of relay IZK, front contact 43 of relay lEULO, and front contact 23of relay IZH to terminal C. Accordingly, the contact G of the signal isclosed so energy is supplied to relay IZLG and its contacts are pickedup.

On interruption of the supply of energy of 120 code frequency to section[2T the relay IZK releases and interrupts the circuit just traced forsupplying energy to the winding of signal IZSL. However, on release ofrelay tinues to be supplied to the signal IZSL over the circuit whichincludes front contacts 46 andv 4'! of relay IZLG and back contacts 40and 4| of relay IZK. The relay IZLG is of a type the contacts of whichare slow to release and they remain picked up for a period longer thanis required for the contacts of relay l2J to pick up. Accordingly, afterrelease of relay lZK the contacts of relay I2LG maintain the supply ofenergy to the winding of signal IZSL until the relay IZUG picks up andits contact 25 interrupts the circuit of the signal I2SL. When the relayIZJ picks up it changes the polarity of the energy supplied to thewinding of signal IZSU from reverse to normal so this signal displays agreen light, while energy is supplied to relay IZUG so that it picks upand cuts off the supply of energy to signal IESL so this signal providesa red light.

If on release of relay |2K prior to picking up of relay |2J the supplyof energy to signal iIZSL were interrupted, this signal would display ared light, while the upper signal IZSU still displays a yellow light sothe signal I28 would momentarily display its approach indicationconsisting of a yellow light over a red light. The arrangement providedby this invention by which the slow releasing relay iZLG maintains thesupply of energy to signal lZSL after release of relay IZK and prior topicking up of relay IEUG prevents the momentary display of the approachindication by the signal on a change from 1-20 to 180 code frequency andinsures that the display of the approach medium indication will bemaintained until the change to the clear indication occurs.

The system of this invention is arranged so that when a train moving inthe reverse direction of trafiic passes through the track stretch thesignals will not momentarily display indications more restrictive thanare required by trafiic conditions.

When such a train enters the section in advance of section IZiT theenergy supplied to section IZ'I' is changed from 180 code frequency to120 code frequency and relay I 2J releases and relay 2K picks up. Onrelease of relay IZJ its contact 33 interrupts the circuit of relayIZUG, but this relay is of a type which is slow in releas- I2K, energyconing so that its contacts remain picked up for a period subsequent torelease of the contacts of relay IZJ. In addition, on release of thecontacts of relay lZJ its contacts 2! and 22 interrupt one circuit forsupplying energy of normal polarity to the winding of signal I ZSU, butenergy of normal polarity continues to be supplied thereto over thecircuit including front contacts 34 and 35 of relay IZUG and backcontacts 2! and 22 of relay IZJ.

On picking up of relay [2K its front contacts 40 and 4| are closed topermit'energy. to be supplied to the winding of signal I ESL when thecontacts of relay I EUY are picked up.

After a short time interval, contacts 34 and 35 of relay I 2UG releaseand interrupt the supply of energy of normal polarity to the winding ofsignal IZSU and establish the circuit to supply mechanism conditions thesignal to display a yellow light, while front contact Y of the signal isclosed so energy is supplied to relay I2U'Y. On the supply of energy torelay IZUY its contacts 27 and 28 pick up and complete the supplyingenergy pick up. I When the relay IZUG releases, its contact 33 codefrequency to section H T, while on picking up of relay IZUY 31establishes the circuit including back contact 38 of relay IZLG, backcontact 30 of relay IZUG, and front contact 31 of relay I 2H forsupplying energy of code frequency to section HT. As soon as the signalIZSL displays its green light and relay I ZLG picks up, contact 38 ofrelay EZLG interrupts the circuit for supplying energy of 120 codefrequency to section HT and establishes a circuit for supplying energyof code frequency thereto. It will be seen, therefore, that in thetimeinterval between the release of relay IZUG and picking up of relayIELG, the supply of energy of 180 code frequency to section HT is cutoil", while energy of 120 code frequency is supplied to section HTduring this time. On interruption of the supply of energy of 180 codefrequency to section HT the relay IiJ, not shown, for that sectionreleases, but the relay HUG, not shown, is slow enough in releasing tomaintain the suprestrictive indication thereby.

The equipment operates in a similar manner on a change from the approachmedium to the I ZLG, like the relay IZUG, is of tacts of which are slowto release, and its contacts remain picked up and maintain the circuitfor supplying energy to the winding of signal |2SL for a periodsubsequent to release of the contacts of relay I2K. After a short timeinterval the relay |2LG releases and its contacts 46 and 41 interruptthe supply of energy to the winding of signal IZSL, while its contact 38interrupts the supply of energy of 180 code frequency to section HT andestablishes the circuit to supply energy of 120 code frequency thereto..On release of the relay |2LG and interruption of the supply of energy tothe winding of signal |2SL the mechanism of this signal conditions theunit to provide its red light 50 signal |2S now displaysits approachindication consisting of a yellow light over a red light.

When the train under consideration enters section |2T relay IZH releasesand its contacts 20 and 23 interrupt the supply of energy to the windingof signal IZSU, so this signal displays a red light, while contact 3| ofrelay |2H interrupts the supply of energy of 120 code frequency tosection |T and establishes the circuit to supply energy of '75 codefrequency thereto. The signal |2S now displays its stop indicationconsisting of a red light over a red light.

From the foregoing it will be seen thatthe system provided by thisinvention is arranged so that changes in the signals either to a lessrestrictive indication or to a more restrictive indication occur withoutobjectionable displays of other indications. Furthermore, it will beseen that this system is arranged so that the supply of coded energy tothe section in the rear of a signal is governed by the signal repeaterrelays so that changes in this energy occur only when the signalsrespond to a change in the signal control relays. i

Construction and operation of system shown in Fig. 2

In Fig. 2 of the drawings there is shown a modification of my inventionadapted for use with signals arranged to provide five aspects. Except ashereinafter pointed out in detail, the system of Fig. 2 is the same asthat shown in Fig. 1. This modification makes use of a special form ofenergy, designated 75M code frequency, to provide an additional proceedaspect. This 75M code may be the usual '75 code to which adistinguishing periodic characteristic which recurs every three cycles,for example, has been added. Suitable decoding means designated 75Mdecoding unit is provided to detect the presence of this code. Thedetails of this decoding means are not essential for an understanding ofthis invention and any appropriate means may be employed for thispurpose. One such means is shown in application Serial No. 452,902 .ofCarl Volz filed July 30, 1942, for Code detecting means. This decodingmeans controls the relay IZHB in such manner that the relay IZHB isenergized when and only when the track relay is responding to energy of75M code frequency.

This modification further differs from that shown in Fig. 1 in that arelay |2LY is provided which is energized when lower signal |2SL isdisplaying a yellow light.

The equipment is shown in the condition which it assumes when the trackstretch is vacant. At this time, venergy of 180 code frequency issupplied to the transformer |2TT and feeds to the track relay IZTR sothat energy is supplied through the decoding transformer |ZDT to relay|2HA and to relay |2J through the resonant rectifier unit |DU.Accordingly, energy of normal polarity is supplied to the winding ofsignal IZSU over the circuit whichis traced from terminal B throughfront contact 20 of relay IZHA, front contact 2| of relay |2J, windingof signal |2SU, front contact 22 of relay |2J, and front contact 23 ofrelay |2HA to terminal C. The signal IZSU, therefore, displays its greenlight, while its contact G is closed to establish the circuit of relayIZUG so that contact 25 of relay |2UG is picked up and interrupts thecircuit of the winding of signal IZSL. The signal |2SL, therefore,displays a red light while the signal |2S displays its clear indicationconsisting of a green light over a red light.

At this time, energy of code frequency is supplied to transformer ||TTover the circuit which is traced from terminal BX through contact I80 ofthe code transmitter I2CT, front contact 30 of relay IZUG, front contact3| of relay I2HA, and primary winding of transformer HTT to terminal CX.

When a train moving in the normal direction of traffic enters section|2T the track relay IZTR ceases to follow code and relays |2HA and |2Jrelease. On release of relay |2HA its contacts 20 and 23 interrupt thesupply of energy to the windingof signal |2SU so this signal displays ared light, while contact 3| of relay |2HA interrupts the supply ofenergy of 180 code frequency to transformer ||TT and establishes thecircuit to supply energy of 75 code frequency thereto. At this time,relay |2UG releases.

When the train'enters section |3T the equipment for that sectionoperates to cause signal I3S to display its stop indication, whileenergy of 75 code frequency is supplied to the transformer IZTT. i

When the train vacates section |2T this energy feeds to relay IZTR whichcauses energy to be supplied through the decoding transformer |2DT torelay IZHA, but not to the other signal control relays. On picking up ofrelay contact 3| interrupts the supply of energy of '75 code frequencyto section HT, while energy of reverse polarity is supplied to thewinding of signal IZSU over the circuit which includes front contacts 20and 23 of relay IZI-IA, back contacts 34 and 35 of relay IZUG, and backcontacts 2| and 22 of relay |2J. Accordingly, the signal |2SU nowdisplays a yellow light, while contact Y of the signal establishes thecircuit of relay IZUY with the result that this relay picks up and itscontact 31 establishes the circuit for supplying energy of 75M codefrequency to section MT. The circuit for supplying energy of 75M codefrequency to section IT is traced from terminal BX through contact 75Mof the code transmitter IZCT, back contact 49 of relay I2LY, frontcontact 3'1 of relay I2UY, back contact 38 of relay IZLG, back contact30 of relay IZUG, front contact 3| of relay IZI-IA, and primary windingof transformer IT to terminal CX.

At this time the upper unit |2SU of signal |2S displays a yellow lightwhile the lower unit |2SL of the signal continues to display a redlight. The signal |2S, therefore, displays its approach indicationconsisting of a yellow light over a red light.

When the train vacatessection |3T, energy of 75 code frequency issupplied to the track relay for that section so that signal |3S displaysits approach indication, while energy of 75M code frequency is suppliedto section l2T. When this IZHA its energy is supplied to the track relayI2TR, energy continues to be supplied through the decoding transformer I2DT to relay IZHA, while energy is also supplied through the 75Mdecoding unit to the relay I ZHB. On picking up of the relay ZHB, energyof reverse polarity is supplied to the Winding of signal I ZSL over thecircuit which is traced from terminal B thrOugh front contact of relayIZHA, back contact of relay IZUG, front contact of relay IZHB, backcontact 41 of relay IZLG, back contact 4| of relay IZK, front contact 28of relay IEUY, winding of signal IZSL, front contact 27 of relay IZUY,back contact 40 of relay I 2K, back contact 46 of relay IZLG, frontcontact 5| of relay IZHB, and front contact 23 of relay |2HA to terminalC. Accordingly, the signal unit |2SL displays a yellow light so thesignal I 28 displays its advance approach indication consisting of ayellow light over a yellow light. In addition, contact Y of signal |2SLestablishes the circuit of relay |2LY and its contact 49 picks up tointerrupt the supply of energy of 75M code frequency to section I IT andcause energy of 120 code frequency to be supplied thereto.

When the train vacates the section in advance of section |3T, energy of75M code frequency is supplied to the rails of section I3T, and theequipment for that section causes energy of 120 code frequency to besupplied to section |2T. When this energy is supplied to the track relayIZTR, energy is no longer supplied through the 75M decoding unit torelay I2HB, but energy is now supplied through the resonant unit IZUDUto relay IZK.

On picking up of relay IZK its contacts 40 and 4| interrupt the circuitfor supplying energy of reverse polarity to signal IZSL and establishthe circuit traced in connection with the system shown in Fig. 1 forsupplying energy of normal polarity to the signal IZSL. The signal unitIZSL now displays a green light so signal |2S displays its approachmedium indication consisting of a yellow light over a green light. Atthis time, contact Y of signal IZSL is opened while contact G is closedand establishes the circuit to supply energy to relay IZLG. When relayIZLG picks up, its contact 38 interrupts the supply of energy of 120code frequency to section I IT and establishes a circuit to supplyenergy of 180 code frequency thereto.

' When the train vacates the second section in advance of section I3T,energy of 180 code frequency is supplied to section |2T with the resultthat relay I 2K releases and relay |2J picks up. When relay |2J picksup, its contacts 2| and 22 change the energy supplied tosignal I2SU fromreverse to normal polarity. Thesignal |2SU now displays a green light,While its contact Y interrupts the circuit of relay IZUY and its contactG establishes the circuit of relay IZUG. Release of relay |2UYinterrupts the circuit of signal IZSL, while this circuit isadditionally interrupted by contact 25 of relay IZUG. The signal |2S nowdisplays its clear indication comprising a green light over a red light.

This modification operates inthe same manner as that shown in Fig. 1 toprevent an objectionable signal flash on a change in the energy suppliedto a section from 120 to 180 code frequency, or from 180 to 120 codefrequency and a detailed description thereof is unnecessary.

This modification also operates toprevent an objectionable signal flashon a change from 120 to 75M code. When energy of 120 code is supplied tosection I2T, relays IZHA and I-ZK aretacts of relay J the contacts ofpicked up so energy of reverse polarity is supplied to signal I ZSU andenergy of normal polary is supplied to signal IZSL. Accordingly, relaysIZLG and |2UY are picked up.

On the change to energy of M code frequency the relay IZK releases andthe relay IZHB picks up. The operating characteristics of the 75Mdecoding means are such, however, that the relay I2HB may not pick upuntil after the relay |2K releases. On release of relay IZK its contacts40 and 4| interrupt one circuit for supply ing energy of normal polarityto the winding of signal IZSL, but the supply of energy of this polarityto the signal is maintained over the circuit which includes frontcontacts 46 and 47 of relay I ZLG, and back contacts 40 and 4| of relayIZK. The signal, therefore, continues to display a green light. Whenrelay IZK releases, its contact 44 interrupts the circuit of relay I2LG,but the relay IZLG is of a type which is slow to release and hence itscontacts remain picked up for a period of time. This period is longenough for the relay |2HB to become picked up. Accordingly, on releaseof the relay |2LG the con- IZHB are pickedup and energy of reversepolarity is supplied to the winding of signal |2SL so that this signaldisplays a yellow light. If the circuit established by front contacts 46and 47 of relay IZLG and back contacts 40 and 4| of relay IZK were notprovided, the signal unit |2SL would be deenergized in the periodbetween release of relay |2K and picking up of relay I2I-IB and woulddisplay a red light so that signal |2S would improperly display itsapproach indication consisting of a yellow light over a red light. Thecircuit provided by the back contacts of relay IZK and the frontcontacts of relay I2LG insures that signal |2SL will continue to displayits green light until the circuit for supplying energy of reversepolarity to the signal is established to thereby insure that the signalwill change from its green to its yellow aspect without delay.

The system of Fig. 2 is also arranged so that r on a change in theenergy supplied to a section from code frequency to 75M code frequency along display of the approach indication is prevented.

When energy of 180 code frequency is supplied section IZT, relays |2HAand |2J are picked up and energy of normal polarity is supplied to theWinding of the signal I2SU. This signal, therefore, displays a greenlight, while its contact G establishes the circuit of relay IZUG so thatthis relay are picked up and its contact 25 interrupts the circuit ofsignal I ZSL.

On the change in the energy supplied to section |2T from 180 to 75M codefrequency the relay |2J releases while the relay I ZHB picks up. Onrelease of relay |2J its contacts 2| and 22 interrupt one circuit forsupplying energy of normal polarity to signal I2SU, but they establishthe circuit including front contacts 34 and 35 of relay I ZUG forsupplying energy of normal polarity to signal IZSU so this signalcontinues to display its green-light. On release of the relay- |2J itscontact 33 interrupts the energizing circuit for relay I ZUG, butbecause of the slow releasing characteristics of the relay |2UG itscontacts remain picked up for a period of timeand maintain the supply ofenergy to the signal IZSU. The relay IZUG is selected so that itscontacts will remain picked up until after the relay |2HB picks up.

Accordingly, on release of relay IZUG therenergy supplied to signal I2SUis changed from normal to reverse polarity, while contact 25 of relayIZUG establishes the circuit to supply energy of reverse polarity to thewinding of signal IZSL. The circuit for supplying energy to signal IZSLis complete as soon as signal I2SU responds to the energy of reversepolarity and establishes the circuit of relay IZUY so that its contactspick up. As a result the signal IZSL will display a yellow light verysoon after signal IZSU displays a yellow light, and the signal [2S willdispay its yellow over red or approach indication for only a very shortperiod.

The system shown in Fig. 2, like that shown in Fig. 1, is arranged sothat the supply of energy to the section in the rear is controlled bythe signal repeater relays so that changes in this energy occur only ifthe signals respond to opera tion of the signal control relays.Similarly, in this modification, the lightout relay IZULO controls thesupply of energy to the winding of the signal l2SL to prevent thedisplay of a green light by this signal when the lamp of the uppersignal unit is burned out.

Construction and operation of system shown in Fig. 3

In Fig. 3 there is shown a modified arrangement which I may employ tocontrol four aspect wayside signals. This modification differs from thatshown in Fig. 1 in that it employs a checking relay OR to control thesupply of energy to the section in the rear. The checking relay GR iscontrolled by the lightout relay, and by the signal control and signalrepeater relays so as to be energized only if the lightout relay isenergized, and if the signal control relays and the signal repeaterrelays are in correspondence. The relay CR, when released, causes energyof '75 code frequency to be supplied to the section in the rear, andprevents the supply of energy of 120 or 180 code to the section in therear.

The system shown in Fig. 3 is shown in the condition which it assumeswhen the track stretch is vacant. At this time, energy of 180 codefrequency is supplied to the rails of section HT and track relay [2TBcauses energy to be supplied through the decoding transformer I2DT tothe relay [2H and through the resonant rectifier unit ISBDU to the relayl2J. As these relays are picked up, energy or normal polarity issupplied to the winding of signal IZSU over the circuit which includesfront contacts 20 and 23 of relay [2H and front contacts 2| and 22 ofrelay I2], and this signal unit displays a green light while its frontContact G establishes the circuit to supply energy to relay I2UG.

At this time, checking relay l2CR is energized over the circuit which istraced from terminal B through front contact 29 of relay 12H, frontcontact so of relay I2J, back contact 6| of relay IZUY, back contact 62of relay IZLG, front contact 63 of relay IZUG, front contact 66 of relayIZULO, nad winding of relay i2CR to terminal C.

Energy of 180 code frequency is supplied to the section in the rear overthe circuit which is traced from terminal BX through contact 180 of thecode transmitter 120T, front contact 66 of relay I2J, front contact 61of relay I203, front contact 3| of relay 121-1, and primary winding oftransformer l ITT to terminal CX.

As the relay [2K is released, its contacts and H interrupt the circuitof signal unit IZSL and it displays a red light, while the signal |2Sprovides its. clear indication consisting of a green over a red light.

When a train moving in the normal direction of traffic enters sectionIZT the track relay I2TR is. shunted and energy is no longer suppliedthrough the decoding transformer I2DT to the relays IZH and l2J. Onrelease of relay I2H its contacts 20 and 23 interrupt the supply ofenergy to :the signal IZSU so that this signal displays its redindication, while its contact G interrupts the circuit of the relayIZUG. In addition, contact 20 and 23 of relay 12H prevent the supply ofenergy to the winding of signal IZSL, while contact 20 of relay l2I-Iinterrupts the supply of energy to relay IZCR, and contact 3| of relay[2H interrupts the supply of energy of 180 code frequency to the sectionin the rear and establishes the circuit for supplying energy of 75 codefrequency thereto. As the signals IZSU and I2SL are both deenergized,the signal I2S displays its stop indication consisting of a red lightover a red light.

At thi time the circuit of relay IZCR. is interrupted and the contact 61of this relay is released.

When the train enters section 1.3T the equipment for that sectionoperates to cause signal B8 to display its stop indication and to causeenergy of '75 code frequency to be supplied to the transformer IZTT.When the train vacates section I2T this energy feeds to the track relayI2TR and it causes energy to be supplied through the decodingtransformer IZDT to relay IZH, but not to relays I2K and IN. When relay12H picks up, its contacts 20 and 23 establish the circuit includingback contacts 2| and 22 of relay-IZJ for supplying energy of reversepolarity to the winding of signal I2SU so this signal displays a yellowlight, while its contact Y is closed so that energy is supplied to therelay IZUY and its contacts pick up and establish a circuit to supplyenergy to the checking relay l2CR. This circuit istraced from terminal Bthrough front contact 20 of relay l2l-I, back contact 60 of relay IZJ,back contact 14 of relay IZK, front contact 13 of relay IZUY, backcontact 12 of relay I2LG, back contact 63 of relay IZUG, front contact64 of relay I2LO, and winding of relay l2CR to terminal C.

When the relay I2H picks up, the back point of contact 3| interrupts thecircuit for supplying energy of 75 code frequency to section HT and thefront point of this contact establishes another circuit including backcontact 61 of relay IZCR for supplying energy of '75 code frequency tosection HT. As soon as the signal IZSU displays its yellow aspect andestablishes the circult of relay I2UY so that its picks up andestablishes the circuit of relay I2CR, the contact 61 of relay I2CRinterrupts the supply of energy of '75 code frequency to section HT andestablishes the circuit for supplying energy of code frequency thereto.This circuit is traced from terminal BX through contact I22 of the codetransmitter l2CT, back contact 16 of relay IZK, back contact 68 of relayI2J, front contact 61 of relay IZCR, front contact 31 of relay I2H, andprimary winding of transformer HTT to terminal CX. At this time,therefore, the signal I2S displays its approach indication consisting ofa yellow light over a red light, while energy of 120 code frequency issupplied to the section in the rear.

i If for any reason on picking up of the relay IZH the signal I2S failsto respond and to dis- P y its y w light, he Checking elay 'ZCR tionIZT. On the supply of this energy to the will not be energized and willmaintain the suprelay iETR, energy continues to be supplied ply ofenergy of 75 code frequency to the section through the decodingtransformer MDT to the in the rear so that a train approaching thesigrelay IZI-I, While energy is now supplied to the relay I2J', but notto the relay lZK.

will receive the most restrictive proceed. indi- On picking up of therelay l2J its contacts 2| cation from the signal for section HT, Whileif and 22' change the polarity of the energy supplied cab signalapparatus is used, alocomotive present to the winding of signal EZSUfrom reverse to in section HT will also receive its most restricnormal,and the mechanism of this signal contive proceed indication in the cab.10 ditions the signal to display a green light, while When the trainadvances far enough to vacate contact Y of the signal interrupts thecircuit of section I3T the equipment for that section oprelay iZUY andcontact G of the signal estaberates to cause signal I38 to provide itsaplishes the circuit of the relay IZUG. preach indication, while energyof 120 code fre- On release of relay IZK its contacts 76 and H quency issupplied to section I2T. When the interrupt the circuit of the windingof signal IZSL track relay I ZTR responds to energy of I code and thissignal displays its red light, While its frequency, energy is suppliedthrough the decontact G interrupts the circuit of relay EZLG. codingtransformer I2DT to the relay I2H and On picking up of relay IZJ orrelease of relay is also supplied through the resonant unit I ZDDU IZK,whichever occurs first, the circuit of relay tothe relay IZK. When thecontacts 10 and 1| 20 20R is interrupted, while after the signals comofrelay [2K are picked up, energy of normal plete their changes, and thesignal repeater reare picked up. On the supply of energy of norfor thisrelay. The relay I2CR is sufficiently slow releasing to remain picked upduring this change in the signals.

G of the signal is closed and energy is supplied On picking up of therelay IZJ its contact 56 On picking up of the relay IZK its contact 16code frequency to section HT, and establishes interrupts the circuit forsupplying energy of anothes circuit for supplying energy of 180 code1210 code frequency to section HT and estabfrequency thereto. lishes acircuit for supplying energy of 180 code If the signals fail to respondto the changes frequency thereto. This circuit is traced from in thesignal control relays, or if the signal reterminal BX through contact180- of the code peater relays fail to respond to the changes intransmitter, front contact 16 of relay IZK, back the signals, thecircuit of the relay lZCR will be contact 53 of relay I2J, front contact61 of relay interrupted and contact 61 of this relay will re- EZCR,front contact 3! of relay 12H, and prilease and cut off the supply ofenergy of 180 a y Winding of transformer HTT to terminal code frequencyto section HT and establish a circuit for supplying energy of 75 codefrequency On picking up of relay [2K its contact 74 inthereto. t upts thp vi u y t a d r uit f r supply This modification employs a lightoutrelay in energy to the relay IZCR, but another circuit I2ULO to checkthe filament of the lamp of the for supplying energy to that relay iscompleted o upper signal IZSU. This relay governs the polarpicking p Ofrelay IZLG- This Circuit is traced ity of the energy supplied to theWinding of the from terminal B through front contact 20 of 15 l r signal|2sL to prevent the display of a relay a a t 60 o relay front greenlight by this signal atatime when the lamp contact. 74 of relay IZK,front contact 11 of of the upper signal. is burned out. The lightoutrelay IZUY, front contact 72 of relay IZLG back relay IZULO alsocontrols the circuit of checking ct 63 o relay g, front Contact of relayI'ZCR so that when the lightout relay is lay IZULO, and Wlndlng relayIZCR to released, relay IZCR is also released and its contermmal h relay15 of a type the tact 6! causes energy of 75 code frequency to be pickedup in the interval between picking up of the contacts of relay 2K andpicking up of relay |.2LG. Accordingly, contact 61 of relay EZCR.remains picked up and maintains the cir cuit for supplying energy of 180code frequency to section HT.

At this timethe signal displays its approach Iii w ii l i :231 1 2 5;?this modification of the medmm mdlcamon nq i of a yellow hg-ht inventionis arranged so that except for the, conof code frequency will besupplied to the section in the rear so that the signal for that sectionwill display its most restrictive proceed indication and a trainapproaching the defective signal will so thatv this relay will releaseand its contact 61 units are Fontroued only by f control will interruptthe circuit for suppplying energy lays This aimngemeni mikes t t o 183.code frequ n y'to section HT! and will for changes m the W i to awaltestablish a, circuit for supplying energy of 75 changes in the upperslgnal t m the reco-de frequency thereto, 70 peater relays for the uppersignal unit, but per- When the train advances far enough to vacate mitsthelower signal unit to respond immediately the. section in advance ofsection I351 energy of to a Change in Portion of the control relay codefrequency is supplied to the rails of sec- As the slgnalumts respondpromptly to n t 'qn 3T and the equipment for t t Section 0pin thecontrol relays, the. signal will not. display crates, tosupnlyenergy of1.80. frequency to sec- 5- ie i na 'e. a p ct on a. change in the signalto the relay IZLG. interrupts one circuit for supplying energy of 180,

. contact 3| of relay its contacts 20 and 23 cut off the control relaysand it. is not necessary to provide means to prevent these signalflashes.

In addition, the checking relay |2CR checks correspondence between ofcoded energy to the section in the rear. This permits the supply ofcoded energy to the section in the rear to be controlled by the signalcontrol relays so that changes in. the energy supplied to the section inthe rear occur promptly.

Construction and operation of system shown in In Fig. 4 of the drawingsthere is shown a modification of this invention adapted for use wherethe wayside signals are arranged to providefive different aspects. Thismodification is similar to that shown in Fig. 3 and employs a checkingrelay CR which is governed by the signal control relays, the signalrepeater relays, and the lightout relays. This modification differs fromthat shown in Fig. 3 in that lightout relays are provided for both theupper and lower signals, while this modification is similar to thoseshown in Figs. 1 and 2 as it employs means governed by the signalrepeater relays to delay changes in the signals. This modification isalso like that shown in Fig. 2 as it employs energy of 75M codefrequency and has means for detecting this energy.

The system of Fig. 4 is shown in the condition which it assumes when thetrack stretch is vacant. At this time, energy of 180 code frequency issupplied to the rails of section |2T and the track relay |2TR causesenergy to be supplied through the decoding transformer |2DT to the relay|2HA and through the resonant rectifier unit IBODU to relay |2J. As-the'relays |2I-IA and |2J are picked up, energy of normal polarity issupplied to the Winding of signal |2SU over the circuit which includesfront contacts 29 and 23 of relay |2HA and front contacts 2| and 22 ofrelay |2J, so signal IZSU provides a green light while its contact Gestablishes the circuit to supply energy to the relay IZUG. At this timethe circuit of the Winding of signal |2SL is interrupted by contacts 50and 5| of relay |2HB so signal |2SL provides a red light and the signalrepeater relays IZLG and The signal |2S, therefore, provides its clearindication consisting of a green light over a red light.

It is assumed that the filaments of the lamps of the signals are intactso the lightout relays |2ULO and |2LLO are both energized. Under theseconditions ergized over the circuit which is traced from terminal Bthrough front contact 2|) of relay |2HA, front contact 60 of relay |2J,back contact 6| of relay IZUY, back contact 62 of relay |2LG, backcontact 85 of relay |2LY, front contact 63 of relay |2UG, front contact64 of relay IZULO, front contact 86 of relay IZLLO, and winding of relayIZCR to terminal C.

At this time, energy of 180 code frequency is supplied to section HTover the circuit which is traced from terminal BX through contact I80 ofthe code transmitter |2CT, front contact 99 of relay |2J, front contact61 of relay IZCR, front IZHA, and primary winding of transformer |TT toterminal CX.

When av train moving in the normal direction of traflic enters section|2T the track relay IZTR is shunted and energy is no longer suppliedthrough the decoding transformer |2DT to the relays IZHA and |2J. Onrelease of relay IZHA |2LY are both released.-

the checking relay |2CR is enthe signal control relays and signalrepeater relays and controls the supply through front contact picked upthe supply of energy supply of energy to the signal |2SU and this signaldisplays a red light, while relay IZUG releases. In addition, at thistime the circuit of relay IZCR. is interrupted and its contact 61releases, while contact 3| of relay |2HA cuts off the supply of energyof 180 .code frequency to section HT and causes energy of '75 codefrequency to be supplied thereto.

At this time, therefore, signal |2S displays its stop indicationconsisting of a red light over a red light, while-energy of '75codefrequency is supplied to the section in the rear.

When the trainenters section |3T the signal for that section displaysits stop indication and energy of 75 code frequency is supplied totransformer |2TT. When the train vacates section |2T this energy feedsto the track relay |2TR and operates it so that energy is suppliedthrough the decoding transformer |2DT to relay |2HA .minal B throughfront contact of relay IZHA,

back contact 34 of relay IZUG, back contact 22 of relay |2J, winding ofsignal |2SU, back contact 2| of relay |2J, back contact 35 of relayIZUG, and front contact 23 of relay |2HA to terminal C. The signal IZSU,therefore, displays a yellow light, and its contact Y establishes .thecircuit of the relay IZUY, while the signal |2S provides its approachindication consisting of a yellow light over a red light.

When the relay -|2UY picks up it completes a circuit for supplyingenergy to the checking relay traced from terminal B 20 of relay |2HA,back contact of relay |2J, back contact 81 of relay 12K, back contact 88of relay |2I-IB, back contact 89 of relay IZLY, front contact 99 ofrelay |2UY, back contact 9| of relay |2LG, back contact 63 of relayIZUG, front contact 64 of relay .I2ULO, front contact 86 of relay IZLLO,and

winding of relay |2CR to terminal C. Accord- |2SU responds in the propermanner and relay IZUY' is energized a circuit for the relay IZCR. willbeestablished.

When the relays |2HA and |2CR. are both of code frequency to section HTis cut off, and energy of IBM code frequency is supplied thereto overthe circuit which is traced from terminal BX through contact 75M of thecode transmitter |2CT,-back contact 94 of relay IZHB, back contact 95 ofrelay |2K, back contact 99 of relay |2J, front contact 61 of relay IZCR,front contact 3| of relay |2HA, and primary winding of transformer ITTto terminal CX.

When the train advances far enough to vacate section |3T the equipmentfor that section operates to supply energy of 75M code frequency tosection IZT. When energy of this frequency is supplied to track relay|2TR energy continues to be supplied through the decoding transformerWhen relay |2HB picks up, its contacts 50 and 5| establish the circuitto supply energy of reverse polarity to the winding of signal IZSL.

This circuit is traced from terminal B through front contact 20 of relay|2HA, front contact 50 of relay IZHB, back contact 41 of relay IZLG,back contact 4| of relay |2K, winding of signal I 2SL,- back contact490f relay 12K; -back'contact 4B of relay IZLG, front contact-Bibi relayI ZHB, and frontcontact-23 of relay IZHA to 'terminal C. Accordingly,the signal I 2SL=will display a yellow light and its contactYwillestablish the circuit of relay -I2LY, while'thesignal IZS now displaysits advance approachindication'consisting of a yellow light overa'yellow light,

When the relay I ZHB picks up, its contact 88 interrupts the previouslytraced circuit for supplying energy to the relay IZCR; but the circuitof this relay is reestablished when relay IZLY relays IZHB and IZLY. Therelay IZCR is slow enough in releasing to remain picked up'throughoutthe interval in which the supply of energy to the relay I ZCR isinterrupted.

On picking up of the relay I2HB its contact 94 interrupts the circuitfor supplying energy of 75M code frequency to section I IT and establishes the circuit for supplying energy of 120 mary winding oftransformer IITT to terminal CX.

When the train adyances farenough to vacate the sectioninadvance'ofsection I3T energyof I code frequency is supplied to sectionI2T and th track relay IZTR operates at a rate'su'ch that energy is nolonger supplied to relay IZHB, but issupplied to relay I 2K, whilerelayIZHA remains picked up. Onpicking up of the relay I'2K 'its contacts 40and 4I cut oif'the supply of energy of reverse polarity to the windingof signal I ZSL and establish the circuit for supplying energy of normalpolarity thereto. This circuit is traced from terminal B through frontcontact 29 of relay IZHA, front contact 42 of relay I ZULO, frontcontact 40 of relay IZK, Winding of signal IZSL, front contact ll ofrelay IZK, front contact 43 of relay IZULO, and front contact 23 ofrelay I 2HA toterminal C. The

lish the circuit to en ity thereto. On release of relay IZK its contactscontact 29 of-relay IZHA, back contact 68. of

relay IZJ, front contact 87 of relay IZK, back contact 97 of relay IZLY, front contact 98 of relay I2UY, 'front contact 9I of relay IZLG,back contact 63 of relay IZUG, front contact 64 of relay l2ULO,'frontcontact 86 of relay IZLLO, and Winding of relay IZCR to terminal C.Therelay IZCR is slow enough in releasing to remain picked up during theperiod in which the circuit of the relay is interrupted,so its contact61 maintains the circuit for supplying energy of 180 code frequency tosection HT.

When the train advances far enough to vacate the secondsection inadvance of section EST energyof 180 code frequency is supplied tosection IZT, and the track relay EZTR operates at a rate such thatenergy is supplied to relay I2J, but is not supplied to relay I'ZK,while energy continues to'be supplied to relay IZHA.

On picking up of relay I2J its contacts 2! and 22 interruptthe supply ofenergy of reverse polarity to the winding of signal EZSU and estabpplyenergy of normal polarwmding of signal IZSL. Accordingly, the signal ofa green light over a red light.

When relay IZJ picksup, its contact '99 interrupts one circuit forsupplying energy of 180 code frequency ,to section II T, and establishesthe other circuit for supplying energy of this he quencyto section I IT.

'As signal IZSU is displaying a green light, re-

'lay IZUY is released and relay I2UG is picked up,

originally traced for this relay.

This modification of the invention includes approach indication.

'When energy of 180 code frequency is supplied I to section IZ' I',relays IZHA and I 2J are picked interrupts 'the circuit for supplyingenergy to signal I ZSL now displays a green light, While the signal, [28displays its approach medium indicanormal P y is pp to the Winding Of snal I2SU over the circuit which includes front contacts 29 and 23 ofrelay IZHA and front concontact Y interrupts the circuit of relay IZLY119C155 2| and 22 f relay As a result of changes in traffic conditionsin relay I2L advance the energy supplied to section I2T may On pickingup of the relay I 2K its contact changed from 00018 frequency o 5Minterrupts the circuit for supplying energyof 120 Code f eq e cy. Onthis change in the energy code frequency to section HT and establishes a0 p d i S c ion ZT, energy is no longer supcircuit forsupplying energyof code frequency thereto. This circuit is traced from terminal iBXthrough contact I89 of the code transmitter 'I ZCT, front contact 95 ofrelay 12K, back contact 99 of relay I-ZJ, front contact 6'! of relaymelt, front cs fieristic occurs on y on v ry three y s, ther contact 3|of relay IZHA, and primary winding of transformer I ITT to terminal'CX.

On picking up of the relay IZK its contact 81 the "relayI-ZCR, whilethis-circuit is additionally '70 pick up until'after the relay E ZJreleases.

interrupted by'contactfBB of relay IZHB when "thatrelay releases.Another'circuit is'es'ta'blislied and 22 of relay l2J for supplying thisenergy. In addition, on release of relay |2J its contact 33 interruptsthe circuit of relay HUG, but the relay IZUG is of a type which is slowto release so its contacts remain picked up and maintain the supply ofenergy of normal polarity to the winding of signal |2SU for a periodsubsequent to the release of relay IZJ. Accordingly, the signal |2SUcontinues to display a green light during the transient interval.

When relay IZHB picks up, energy of reverse polarity is supplied to thewinding of signal |2SL over the circuit which is traced from terminal Bthrough front contact 2|! of relay IZHA, front contact 50 of relay I2HB,back contact 41 of relay |2LG, back contact 4| of relay |2K, winding ofsignal I2SL, back contact 40 of relay IZK, back contact 46 of relayIZLG, front contact 5| of relay IZHB, and front contact 23 of relayIZI-IA to terminal C. The signal |2SL, therefore, displays a yellowlight.

On release of the relay IZUG the supply of energy of normal polarity tosignal IZSU is cut ofi and energy of reverse polarity is suppliedthereto over the circuit which includes back contacts 34 and 35 of relayIZUG and back contacts 2| and 22 of relay |2J. Accordingly, the signalIZSU displays a yellow light instead of a green light, and as the upperand lower units of signal |2S both display yellow lights the signalprovides its advance approach indication.

The various parts of the apparatus are arranged and selected so that thecontacts of relay |2UG remain picked up to cause signal TSSU to continueto display a green light until signal IZSL has been conditioned todisplay its yellowlight. This prevents the possible momentary display ofa yellow over a red light by the signal |2S at this time. Such a signalwould be interpreted by the engineman of an approaching train asindicating less favorable traffic conditions than actually exist andmight cause him to unnecessarily effect an emergency applicalion of thebrakes. This system prevents the momentary display of the approachindication at these times and thus eliminates possible delays in trainmovements.

The equipment operates in a similar manner to prevent a momentarydisplay of the approach indication on a change in the signal aspect fromthe approach medium to the advance approach indication.

When energy of 120 code frequency is supplied to section IZT, the relaysIZHA and IZK are picked up, while energy of reverse polarity is suppliedto the winding of signal |2SU, and energy of normal polarity is suppliedto the winding of signal |2SL. As the signal IZSL displays a green lightits contact G establishes the circuit of the relay I2LG.

When the energy supplied to section I2T is changed from 120 to 75M codefrequency the relay |2K releases and the relay IZHB picks up. On releaseof relay |2K its contacts and 4| interrupt one circuit for supplyingenergy of normal polarity to the winding of signal IZSL, but theyestablish a circuit including front contacts and 41 of relay |2LG forsupplying energy of normal polarity to the signal IZSL so this signalcontinues to display a green light.

On release of relay IZK its contact M interrupts the circuit of relayI2LG, but the relay |2LG is of a type the contacts of which are slow tore-.

lease so they remain picked up after release of relay IZK and maintainthe supply of energy to the winding of relay I2SL.

On picking up of relay IZHB its contacts 50 and 5| establish the circuitto supply energy of reverse polarity to the winding of signal |2SL onrelease of relay IZLG. Accordingly, on release of relay I2LG the supplyof energy of normal polarity to the winding of signal |2SL is cut off,but energy of reverse polarity is supplied thereto so the mechanism ofsignal |2SL immediately conditions the signal to display a yellow lightinstead of a green light, and the signal |2S now provides its advanceapproach indication consisting of a yellow light over a yellow light.

The various parts of the apparatus are arranged and selected so that onthe change in the energy supplied to section |2T from120 to M codefrequency the relay |2LG remains picked up until after the relay IZI-IBpicks up. This insures that on release of relay |2LG and consequentcutting off of the supply of energy of normal polarity to signal IZSL,energy of reverse polarity will be supplied thereto and the signal willdisplay a yellow light and there will be no time interval during whichthe signal displays a red light.

If the circuit including the front contacts 45 and 41 of relay IZLG forsupplying energy of normal polarity to the signal IZSL is not pro vided,the signal winding will be deenergized if relay IZK releases beforerelay I ZHB picks up. Under such circumstances the signal |2SL willdisplay a red light until the relay |2HB picks up and during thisinterval the signal IZS will display its approach indication consistingof a yellow light over a red light. This is a more restrictiveindication than is required by trafhc conditions and may unnecessarilydelay traffic. The system of this invention eliminates the momentarydisplay of the approach indication and thus prevents trafiic delays.

In the modification shown in Fig. 4 the circuit for supplying energy tochecking relay IZCR, is controlled by contacts of the lightout relaysfor both the upper and lower signal units so that if the lamp of eitherof these units is burned out the checking relay |2CR will be releasedand will cause the energy supplied to section ||T to be of 15 codefrequency. Accordingly, under these conditions the signal for section Twill display its most restrictive proceed indication and trains willapproach the defective signal at reduced speed.

Similarly, if for any reason there is a disagreement between the signalcontrol relays and the signal repeater relays, the circuit of the relay|2CR will be interrupted and this relay will cause energy of 75 codefrequency to be supplied to section MT.

The modification shown in Fig. 4, like the other modifications of theinvention, has the circuit for supplying energy to the winding of signal|2SL controlled by the lightout relay IZULO to prevent the supply ofenergy of normal polarity to this signal, and consequent display of agreen light by this signal, at a time when the lamp of the upper signalIZSU is burned out.

Although I have herein shown and described only four forms of railwaysignaling systems embodying my invention, it is understood that variouschanges and modifications may be made therein within the'scope of theappended claims without departing from the spirit and scope of myinvention.

Having thus described my invention, what I claim is:

1. In combination, a section of railway track, a control relay governedby traffic conditions in said section, a slow releasing relay, a lightsignal for said section, saidsignal being of a type whichhas a memberbiased to a first position in which it conditions the signal to provideone indication and having a Winding eiiective when energized to movesaid member to a secondposition in which it conditions the signal toprovide a different indication and establishes a circuit to supplyenergy to said slow releasing relay pr videdsaid control relay is pickedup, a circuit controlled by a front contact of said control relay forsupplying energy to the winding of said signal, and a second circuitcontrolled by a front contact of said slow releasing relay for alsosupplying energy to the winding of said signal.

2. In combination, a section of railway track, a control relay governedby traffic conditions in said section, a slow releasing relay, 9, lightsignal for said section, said signal being of a type which has a memberbiased to a first position in which it conditions the signal to provideone indication and having a winding eifective when energized to movesaid member to a second position in which it conditions the signal toprovide a different indication and establishes a circuit to supply en- 1ergy to said slow releasing relay provided said control relay is pickedup, a circuit controlled by a front contact of said control relay forsupplying energy to the winding of said signal, and a second circuitcontrolled by a front contact of said slow releasing relay and a backcontact of said control relay for also supplying energy to the windingof said signal.

3. In combination, a section of railway track, a control relay governedby traffic conditions in said section, a slow releasing relay, a lightsignal for said section, said signal being of a type which has a memberbiased to a first position in which it conditions the signal to providea first indication and having a, winding efiective when supplied withenergy of reverse polarity to move said member to a second position inwhich it conditions the signal to provide a second indication and whensupplied with energy of normal polarity to move said member to a thirdposition in which it conditions the signal to provide a third indicationand establishes a circuit to supply energy to said slow releasing relayprovided said control relay is picked up, a circuit including backcontacts of the control slow releasing relay for supplying energy of'reverse polarity to the winding of said signal, a circuit including afront contact of the control relay for supplying energy of normalpolarity to the winding of said signal, and a front contact of said slowreleasing relay and a back contact of said control relay for alsosupplying energy of normal polarity to the winding of said signal.

4. In combination, a section of railway track, a control relay governedby traffic conditions in said section, a slow releasing relay, a lightsignal for said section, said signal being of a type which has a memberbiased to a first position in which it conditions the signal to providetion and having a winding efiective when supplied with energy of reversepolarity to move said member to a second position in which it conditionsthe signal to provide a second indication and when supplied with energyof normal plarity to move said member to a third position in which itconditions the signal to provide a third indication and establishes acircuit to supply energy to said slow releasing relay provided saidcontrol relay is picked up, a circuit including relay and of saidcircuit including a a first indicaverse polarity to move said backcontacts of the control relay and of said slow releasing relay forsupplying energy of reverse polarity to the winding of said signal, acircuit including a front contact of the control relay 7 for supplyingenergy of normal polarity to the winding of said signal, and a circuitincluding a front contact of said slow releasing relay for alsosupplying energy of normal polarity to the winding of said signal.

5. In combination, a section of railway track, a first control relaygoverned by traffic conditions in said section, a second control relaygoverned by trainc conditions in advance of said section, a slowreleasing relay, a light signalforsaidsection, said signal being of atype which has a member biased to a first position in which itconditions the signal to provide a first indication and having a windingeffective when supplied with energy of reverse polarity to move saidmember to a second position in which it conditions the signal to providea second indication and when supplied with energy of normal polarity tomove said member to a third position in which it conditions the signalto provide a third indication and establishes a circuit to supply energyto said slow releasing relay provided the second control relay is pickedup, a, circuit including a front contact of the first control relay andback contacts of the second control relay and of the slow releasingrelay for supplying energy of reverse polarity to the winding of saidsignal, a circuit including front contacts of the first and secondcontrol relays for supplying energy of normal polarity to the winding ofsaid signal, and a circuit including front contactsof the first controlrelay and the slow releasing relay for also supplying energy of normalpolarity to the winding of said signal.

6. In combination, a section of railway track, a signal for said tracksection, said signal being of a type having a member biased to a firstposition inwhich it conditions the signal to provide a first indication,said signal having a winding effective when energized with current ofremember to a second position in which it conditions the signal toprovide a second indication and establishes a circuit to supply energyto a first repeater relay, said winding being efiective when energizedwith current of normal polarity to move said member to a third positionin which it conditions the signal to provide a third indication andestablishes a circuit to supply energy to a second repeater relay, afirst control relay governed by traffic conditions in said section andcontrolling the supply of energy to the winding of said signal, a secondcontrol relay governed by traffic conditions in advance of said sectionand controlling the polarity of the energy supplied to the winding ofsaid signal in such manner that energy of reverse polarity is suppliedto the signal winding when said relay is released and energy of normalpolarity is supplied to the signal winding when said relay is picked up,a checking relay, a circuit for supplying energy to said checking relaywhen the first control relay'is picked up provided the first repeaterrelay is also picked up and the second control relay and the secondrepeater relay are released, a circuit for also supplying energy to saidchecking relay when the first and second control relays are picked upprovided the first repeater relay is released and the second repeaterrelay is picked up, and means including said checking relay forcontrolling trafiic approaching said section.

- advance of said section indication and having energized with currentnal to provide '7. in combination with a section of railway track, meansgoverned by traffic conditions in for at times supplying to the rails ofsaid section coded energy of afirst character and at other times of asecond character, a code following track relay receiving energy over therails of said section, a first and a second control relay associatedwith said track relay, means effective when the track relay isrespondingto energy of either character to energize the first controlrelay and effective only when the track relay is responding to energy ofthe second character to energize the second control relay, a signal forsaid section, said signal being of, a type having a member biased to afirst position in which it conditions the signal to provide a firstwinding effective when of reverse polarity to move said member to asecond position in which it conditions the signal to provide a secondindication and to establish a circuit to supply energy to a firstrepeater relayand effective when energized with current of normalpolarity to move said member to a third position in which it conditionsthe signal to provide a third indication and establishes a circuit tosupply energy to a second repeater relay, a checking relay, a circuitincluding front contacts of the first control relay and the firstrepeater relay and back contacts of the second control relay and thesecond repeater relay for supplying energy to said checking relay, acircuit including front contacts of first and second control relays andof the second repeater relay and a back contact of the first repeaterrelay for also supplying energy to said checking relay, and meanscontrolled by said checking relay for governing traffic approaching saidsection.

8. In combination with a section of railway track, means governed bytraffic conditions in advance of said section for at times supplying tothe rails of said section coded energy of a first character and at othertimes of a'second character, a code following track relay receivingenergy over the rails of said section, a first and a second controlrelay associated with said track relay, means effective when the trackrelay is responding to energy of either character to energize the firstcontrol relay and effective only when the track relay is responding toenergy of the second characterto energize the second control rela asignal for said section, said signal being of a type having a memberbiased to a first position in which it conditions the siga firstindication and having a winding effective when energized with current ofreverse polarity to move said member to a second position in which itconditions the signal to provide a second indication and to establish acircuit to supply energy to a first repeater relay andeffective whenenergized with current of normal polarity to move said member to a thirdposition in which it conditions the signal to provide a third indicationand establishes a circuit to supply energy to a second repeater relay, achecking relay, a circuit including front contacts of the first controlrelay and the first repeater relay and back contacts of the secondcontrol relay and the second repeater relay for supplying energy to saidchecking relay, a circuit including front contacts of first and secondcontrol relays and of the second repeater relay and a back contact ofthe first repeater relay for also supplying energy to said checkingrelay, said signal including a lamp, a lightout relay energized inseries with said lamp and having a contact included in series with eachof the circuits for supplying energy to said checking relay, and meanscontrolled by said checking relay for governing traific approaching saidsection.

9. In combination with a section of railway track, means governed bytraffic conditions in advance of said section for at times supplying tothe rails of said section coded energy of a first character and at othertimes of a second character, a code following track relay receivingenergy over the rails of said section, a first and a second controlrelay associated with said track relay, means effective when the trackrelay is responding to energy of either character to energize the firstcontrol relay and effective only when the track relay is responding toenergy of the second character to energize the second control relay, asignal for said section, said signal being of a, type having a memberbiased to a first position in which it conditions the signal to providea, first indication and having a winding effective when energized withcurrent of reverse polarity to move said member to a second position inwhich it conditions the signal to provide a second indication and toestablish a. circult to supply energy to a first repeater relayandeffective when energized with current of normal polarity to move saidmember to a third position in whichit conditions the signal to provide athird indication and establishes a circuit to supply energy toa secondrepeater relay, a checking relay, a circuit including front contacts ofthe first control relay and thefirst repeater relay and back contacts ofthe second control relay and the second repeater relay for supplyingenergy to said checking relay, a circuit including front contacts offirst and second control relays and of the second repeater relay and aback contact of the first repeater relay for also supplying energy tosaid checking relay, a circuit including a back contact ofthe firstcontrol relay for supplying coded energy of the first character to therails in the rear of said section, andacircuit including a front contactof the first control relay for supplying to the rails in the rear ofsaid section coded energy of the first or second character according assaid checking relay is released or picked up respectively.

10. In combination, a section of'railway track, a first and a secondcontrol relay, means governed by traffic conditions in said section andin advance of said section for at times supplying energy to said firstcontrol relay and at other times supplying energy to said second controlrelay, a slow releasing relay, a signal for said section having an upperand a lower unit, each of said signal units being of a typehaving amovable member biased to a first position in which it conditions theunit to provide one aspect and having a winding effective when energizedto move said member to a second position in which it conditions saidunit to provide a second aspect, a circuit including a front contact ofsaid first control relay for supplying energy to the winding of saidupper signal unit, and a circuit including a front contact of said firstcontrol relay and a contact of said upper signal unit closed only whenthe movable member of said signal unit is in its second position forsupplying energy to said slow releasing relay, said slow releasing relaybeing effective when picked up to establish a circuit to also supplyenergy to the winding of said upper signal unit, said second controlrelay being effective when energized to establish a relay maintains thesupplyof energy to the Winding of the upper signal unit until the secondcontrol relay becomes energized.

11. In combination," a section of railway track, a first and a secondcontrol relay; means gov- "ernedby trafiic conditions in saidsection-and in controlled by a front contact of said control readvanceof said section for at times supplying en- I ergy to thefirst controlrelay and'at other times "supplying energy to the'second control relay,a

signal for said section having an'upp'er and a lower unit, each of saidsignal units being of a type which has a member biased to a firstpositionin which it conditions the signal unit to provide one aspect andhaving a winding efiective when energized to move said member to asecond position in whichrit conditions the' signal unit to'provide asecond aspect, a first and a second slow releas-.-

ing relay, a circuit including a'front contact of the first controlrelay for' supplying energy to the winding of said upper signal unit,acircuit including a front contact of saidfirst control relay" and acontact of said uppersignal unit closed only when the movable member of"said unit is in its'second positionfor supplying energy to the firstslow releasing relay, a' circuit including front contacts "of said firstslow releasing relay for also supplying energy to the winding of said:upper signal unit, a circuit including a front contact of said secondsignal control relayfor supplying energy to the winding of" said lowersignal unit, a circuit including afront contact lay 'for'supplyingenergy to said-operating winding; a second circuit controlled by afront'con- 'tact'ofsaid slow releasing relay for also supplying energyto said operating winding, and means controlled by said slow releasingrelay for governing traflic approaching said section.

13. In combination with a section of railway track, a signal for saidsection having an-upper and a lower unit each having a lamp, each ofsaid units having a'member'biased to a first position in which itconditions the associated unit to display a first indication, each unithaving an operating Winding eifective when energized with current of onepolarity to move said member to a second position in which it conditionsthe unit to display a second indication and effective when energizedwith current of the other polarity to "move said member to a thirdposition in which it conditions the unit to display a third indication,means governed by trafiic conditions for at times supplying energy ofsaid one polarity and for at other times supplying energy of said otherpolarity to the winding of said upper unit and for at both said timessupplying energy to the winding of said lower unit, a lightout relay forchecking the integrity ofthe lamp of one of said units, and meanscontrolled by said lightout relay effective when 'a defect occurs in theassociated lamp for preventing the supply of energy of said otherpolarity to the other unit.

of said second signal controlrelay and a contactof said lower signalum't closed only when the movable member of said unit is in its secondposition for supplying energy'to'said's'econd slow releasing relay,j'and a circuit including a front, contact of said'second slowreleasing-relay-for also supplying e ergy to the winding of said lowersignalunit.

12. In combination-with'a sectionof railway track, a control relaygoverned'by trafiicccndi tions in said section/a" slow releasing relay,a light signal for said section',-said signal having 'a member biasedtoa first-position in which it conditions the signal to display oneindication and having an operating winding 'efiec'tive when it energizedto move said member to-a second--po-' sition in which it conditions thesignal to display a different indication and establishes acircuit forsupplying energy to said slow releasing-relay provided said controlrelay is picked up, a circuit '14; In combination with a section ofrailway track, a signal for said section having an upper and a'lowerunit each having a lamp, each of said units having a member biased to afirst position in which it conditions the associated unit to display afirst indication, each unit having an operating Winding efiective whenenergized with current of one polarity to move said member to a secondposition in which it conditions the unit to display a second indicationand effective when energized with current of the other polarity to movesaid member to a third position in which it -conditions the'unittodisplay a third indication,

means governed by trafiic conditions for at times supplying energy ofsaid one polarity and for at other times supplying energy of said otherpolarity tothewinding of said upper unit and for at both saidtimessupplying energy to the winding or said lower unit, a lightoutrelay for checking the integrity of the lamp of said upper unit, andmeans controlled by said lightout relay effective when-a defect occursin the associated lamp for preventing the supply of energy of said otherpolarity to thelower unit to thereby prevent the display of a proceedindication by said lower unit. .7 e

RALPH R. KEMMERER.

